<?php
//$arr = array (20, 1, 5, 10, 7, 16);
$arr = array (-32,-15,4,6,-14,613,4,63,6,4);
$diff = INF;
foreach ($arr as $item0) {
	foreach ($arr as $item1) {
		$localdiff = abs($item0 - $item1);
		if ( $localdiff > 0 && $localdiff < $diff ) {
			$diff = $localdiff;
			$keep0 = $item0;
			$keep1 = $item1;
		}
	}
}

echo "Smallest distance was $diff, between $keep0 and $keep1";
?>